The present invention relates to a dumbbell for use in various kinds of sports, and more particularly to a flexible dumbbell suitable for use in physical exercises, running or the like.
A conventional dumbbell is made of cast iron, which is used by grasping the central portion thereof to train muscles of a wrist, an arm, a shoulder and the like. In case a user grasps one end of the dumbbell and swings its other end at a constant rhythm in a vertical direction, he will feel a pain at his carpal bones due to excessive weight of the dumbbell acting on his arm joint. In case a user grasps the central portion of the dumbbell and swings it in running, the weight load of the dumbbell acting on his wrist, arm and shoulder will increase due to his feet impacting on the ground to cause muscle binding of his swing arm. For these reasons, the dumbbell of cast iron is unsuitable for use in physical exercises, running and the like. Furthermore, the dumbbell of cast iron will injure the user's hand or an adjacent instrument in its careless use, and in winter the user will hesitate to use the dumbbell of cast iron because of a cold feel.